The present invention relates generally to the preparation of an improved partial phosphate ester formulation for the surface treating of metallic articles, including both ferrous and non-ferrous articles, wherein a single formulation may be employed for the concurrent operations of cleaning, de-greasing, de-scaling, and polishing of the article. Agitation of the metal articles is obtained in a conventional barrel or vibratory finishing machine wherein the articles are immersed and agitated through either tumbling or vibration, and may, in certain instances, be immersed in a media such as an abrasive media.
At the present time, various formulations of chemical compositions have been utilized for the purpose of conducting single operations on metal articles in order to achieve a desired surface finish. For example, those compositions most frequently employed include sodium or potassium hydroxide, phosphates, carbonates, silicates, clays, soaps, and the like. While each of these materials may perform certain of the operations in a functional fashion, such as, for example, either cleaning, de-greasing, de-scaling or polishing, the materials nevertheless required the use of multiple step treatment.
The quality of the finish obtained on the metal surface has been primarily influenced by the performance of the various soaps, primarily those soaps derived from animal tallow, coconut oil, or other triglycerides, with these materials having been utilized primarily in barrel or vibratory metal finishing machines.
As indicated, a plurality of individual steps has normally been required in order to obtain acceptable metal surface finishes. Soaps and soap-containing products frequently produce undesirable side effects due to their behavior in hard water, including the formation of soap scum with calcium bicarbonates, poor water rinsibility, slow polishing action, as well as a partial congealing of the cleaning medium. On some occasions, the free alkalinity present in the soap products due to the manufacturing techniques employed presented some difficulties in treating of certain surface finishes, such as aluminum.
As a result of these difficulties, many synthetic or natural metal finishing media have been utilized in order to accomplish a shortening of the processing time, as well as processing steps and operations required. These various materials which have been employed have been found, however, to be inadequate either for accomplishing the entire surface treatment operation in a single batch operation, or in accomplishing the task in a reasonable period of time.
Typically, a barrel finishing machine is an apparatus with either an open or closed hexagonal or similarly shaped enclosure. These finishing machines are available in varying sizes, depending upon the application, and are arranged to rotate in one operational direction at a controllably variable speed. The rotational speed is normally selected as a function of the compartment size, the volume of parts and weight present in the charge, as well as the media ratio being employed. Other parameters include the type of material utilized in the surface treatment material, the water volume present, as well as the processing time normally available.
Vibratory finishing machines, which are also conventionally employed, normally utilize an open housing or the like equipped with a variable speed drive arranged to oscillate the housing at a certain frequency, ranging for example, from several hundred of cycles up to several thousands of cycles per minute. The parameters present which determine the proper drive frequency include the compartment size, the type of parts as well as weight of parts present, the media ratio such as an abrasive media when employed, the type of material employed as the surface treatment composition, as well as the processing time available. Both barrel finishing machines and vibratory finishing machines are commercially available.
As has been indicated, several individual operations or steps are normally employed in order to achieve the desired surface finish. These steps are identified briefly as follows:
Step 1 -- Clean the product, including de-greasing, deburring and de-scaling (cleaning media optionally present). PA1 Step 2 -- Rinse. PA1 Step 3 -- Utilize neutralizer rinse in case de-scaling formulation employed. PA1 Step 4 -- Rinse. PA1 Step 5 -- Burnish or polish, media being optionally present. PA1 Step 6 -- Rinse.
The above listing indicates the minimum steps required to obtain a polished effect on the surface of a metal part. The time required for each of these individual operations may vary from several minutes up to several hours, depending upon the condition of the non-treated product, the surface finish desired, and the nature of the finished product. In other words, the characteristics of the part being treated will normally determine the processing time.